RU2803126C2 - Hollow fibre membrane for liquid filtration - Google Patents

Abstract

FIELD: liquid filtration technology.

SUBSTANCE: group of inventions relates to membranes, the modules of which have built-in antibacterial properties with the configuration of the movement of the filtered material from the periphery to the centre. The membrane can be used in portable water filtration devices in multi-purpose installations operating under pressure in the suction pipeline, with a pressurized water line or under the gravity head of the liquid. Disclosed is a hollow fibre membrane having inherent antimicrobial properties for liquid filtration, comprising a plurality of porous hollow membrane fibres, wherein the hollow membrane fibres comprise a polymer or mixture of polymers comprising an antimicrobial substance physically enclosed and chemically bonded at the site of cross-linking between the polymer chains, imparting an antimicrobial effect to the fibres, and at the same time, the hollow fibre membrane is designed so that the liquid flows outside the fibres of the membrane and passes through the porous membrane into and along the cavity of the fibres, so that the retentate remains outside the membrane, and so that the filtered liquid (filtrate) flows out of the hollow end of the fibres. In another embodiment, a method is provided for manufacturing a hollow fibre membrane having inherent antimicrobial properties, comprising the following steps: a) blending an antimicrobial-embedded polymer or polymer blend with an antimicrobial-embedded agent with a polymer or polymer blend without the antimicrobial agent, with a pore former containing polyethylene glycol and other additives, with solvent for all components; b) passing the mixture obtained in step a) through a spinneret together with a polymer precipitant. Also presented is a device for filtering a liquid, containing a hollow fibre membrane, and the device includes a housing for the membrane, where the housing contains at least one supply channel and at least one drain channel.

EFFECT: group of inventions improves the quality of filtered water and water flow, reduces the required suction pressure, passage pressure or gravitational pressure.

34 cl, 9 dwg, 3 tbl, 3 ex

Description

TECHNICAL FIELD OF THE INVENTION:

This invention belongs to the field of liquid filtration technology, for example, these are membranes whose modules have built-in antibacterial properties with a configuration for the movement of the filtered material from the periphery to the center. The membrane can be used in portable devices for filtering water in multi-purpose installations operating under pressure in a suction pipeline, with a pressurized water line or under gravitational fluid pressure. In particular, an exemplary embodiment of the present invention also relates to hydrophobic outer sides or outer walls of a hollow fiber and hydrophilic inner walls of a hollow fiber membrane with excellent long-term water permeability and without additional flushing.

HISTORY OF INVENTION

Clean drinking water has always been in demand all over the world. 663 million people depend on unimproved water sources, and 160 million depend on surface water. Worldwide, at least 2.1 billion people use drinking water sources contaminated with excrement. Contaminated water can carry disease and cause diarrhea, cholera, dysentery, typhoid and polio. About 842,000 people die each year from diarrhea due to contaminated drinking water, sanitation and hand hygiene. Diarrhea is a preventable disease, as is the 361,000 children under 5 who die each year due to the above-mentioned problems. Nearly 240 million people suffer from acute and chronic bilharzia, caused by parasitic worms transmitted from water sources, according to research from the World Health Organization.

In Pakistan, 44% of the population does not have access to clean drinking water during their lifetime. In 2015, 311 children died in Tara alone due to lack of clean drinking water. In Khyber Pakhtunkhwa and the Federally Administered Tribal Areas (FATAs), 40% of deaths are due to water-borne diseases. Every minute a child dies due to contaminated water in Pakistan. There are 1 million cases of diarrhea per year in Pakistan. Pakistan is currently spending $1.3 billion to eliminate water-borne diseases. According to the World Health Organization, 25-30%) of Pakistanis are admitted to hospital due to water-borne bacteria, and 60% of all infant deaths are due to contaminated water sources.

Clean water is a big problem at the household and at the individual level. For people without permanent residence, water is a very expensive resource. There is a need for a device that can filter any water on site when required. On average, more than 70% of freshly available water is contaminated and unsuitable for drinking. Current technologies used to filter water are too expensive, not portable, require a lot of power, or don't last long.

During natural disasters, emergencies, accidents, rescue services or the military use disinfectant medications, coagulating tablets or, if possible, install a water filtration unit. The first two options are not effective enough and are unreliable, since they are harmful to the human body, and the last option is too expensive. The supply of clean water is also quite difficult.

Traditional water filtration membranes use a lot of electricity to pump water through the membrane. These membranes have pores of undefined or large sizes, which typically result in biological contaminants leaking out the other side of the membrane into the treated water. Therefore, many existing membrane water filtration systems are equipped with either ultraviolet light, ozonation or chlorination (for disinfection). The first two options require power, and the latter has a carcinogenic effect on the human body.

Filters based on sand/granite/carbon/adsorbent substrates have low filtration rates and low levels of productivity in terms of eliminating biological contaminants (especially viruses). To produce filtered water on a mass scale, a larger installation is required, as well as a constant change of absorbent to maintain a high filtration rate. A post-treatment facility is also required to remove remaining biological contaminants.

Ceramic membranes used for portable water filtration devices are not durable enough. They are quickly damaged upon impact and weigh much more. Also, their production requires high temperatures. It is quite difficult to achieve the appropriate pore size in such membranes to effectively remove biological pollutants. The sintering process used to produce ceramic membranes is not well established to reduce pore sizes to 20 nm and below.

Hollow fiber membranes are widely used in the domestic and industrial sectors for microfiltration and ultrafiltration. As water passes from one side through the membrane to the other side, a filtration process occurs that allows only water molecules and particles that are smaller than the pore size of the membrane to pass through. Thus, the surface of the membrane and the thickness of the fiber create a boundary that separates unfiltered water from filtered water. Polyethylene, cellulose acetate, polysulfone, polyvinylidene fluoride, polycarbonate, polyacrylonitrile, etc. used as a material to create membrane fibers. This method requires high porosity of hollow fibers and small pore size to improve the filtration process and its accuracy. Also, the membrane must have pores of the appropriate size suitable for the filtration object to effectively eliminate bacteria, retention of solids and dense components. At the same time, membrane fibers must have high strength and water permeability to ensure long-term use in chemically polluted environments and high operating pressures. Since existing hollow fiber membranes and the above materials were developed to improve the filtration process, some inconsistencies were found. For example, standard hollow fiber membranes provide poor filtration performance, require backwashing, and can be contaminated with bacteria and other microorganisms.

Several unsuccessful attempts have been made to solve the problems described above, for example, it was proposed to increase the porosity of the membranes. But hollow fiber membranes with high filtration efficiency, microbiocidal properties and long-term stability have not yet been developed.

Currently, three filtration technologies are used: 1) Ultrafiltration (UF) 2) Nano filtration 3) Reverse osmosis filtration. The most common membranes for fresh water are ultrafiltration membranes. Current portable hollow fiber membranes rely on UV technology and therefore cannot effectively remove liquefied metals such as arsenic, chromium, iron, etc. To effectively remove such metals, it is necessary to reduce the pore size to 2 nm or less.

On the other hand, it is often practiced to increase the pore diameter of the membrane for greater water permeability and productivity, but this in turn leads to deterioration of the membrane's fractionation ability and its strength.

Hollow fiber membranes are commonly used for microfiltration and ultrafiltration of water. Such modules are used in a variety of applications: from large industrial-scale plants to portable water filters. One configuration of a hollow fiber membrane module known to us is shown in US 4,435,289, where porous hollow fibers are sealed in a cured resin at both ends of the fibers, which also serves as support for the membrane. Water enters the fibers from the holes at the ends of the membrane and moves inside, and then a filtration process occurs when the water flows through the micropores of the walls of the hollow fibers. This is a filter element with a reverse flow direction, where clean water moves through the gaps of the fibers, and the filtrate is formed on the inside of the fibers. Such fibers are cleaned by flushing water through the interior of the fibers and possibly rewashing or backwashing as described in WO 2008/101172 by Vestergaard Frandsen.

This principle is also explained by the concept of drinking straws, as described in EP 2235502 B1. This device contains an oral mouthpiece used to suck water through a tube containing a certain number of hollow fibers in a staple form with microporous membrane walls that are supported by both ends sealed at the top under the mouthpiece. When a person sucks water into his mouth, the flow of water goes from the outside to the inside. The filtrate remains outside the membrane walls, and clean water passes through the outer fibers through the microporous walls. Then, clean water comes out through the sealed ends near the drinking mouthpiece.

This device is described in EP 2235502 B1 and faces a common problem with such filters: hollow fibers are made of a hydrophilic material that delivers water through the membrane, forming a non-slip layer of water on it. Due to this phenomenon, air cannot (or practically cannot) pass through the membrane walls when they are wet (for example, when they are used to filter water). This risks trapping large amounts of air near the fibers, which reduces water flow as air prevents it from passing through the membrane. In this regard, more powerful water pumping is necessary to obtain optimal flow from the module.

This is a fairly common problem in this type of filtration device and a solution to this problem has been proposed previously, as stated in the previously mentioned section of US 4,636,307, several hydrophobic fibers are added to the module to repel water and form a non-slip layer around the fibers to prevent air penetration. However, in terms of production, this is a complex and expensive solution.

Instead of arcuate hollow fibers in the membrane module, a different configuration can be used, a module that extends into the inlet water chamber, with fibers that have an open end that is supported and sealed at the top of the device, and a closed end that extends into the inlet water chamber, as described in EP 0938367 and EP 2235502 B1. The principle is similar and creates the same problem.

Another configuration is described in US 2004/078625, where two arcuate membrane modules are located in one pipe and the bent parts are turned towards each other. Water flows from the inside to the outside from the first module, the open ends of which are supported and sealed near the mouthpiece. The system is susceptible to air accumulation in the compartment between the two modules, which may result in poor water flow or the need to increase pressure when pumping water.

Unlike the configuration described above, the method described in US 8,852,439 B2 uses a single arcuate hollow fiber module to avoid air entrapment in the hydrophilic fibers. The open ends are supported and sealed near the mouthpiece, while the bent parts face the mouthpiece. This configuration is the reverse of that described in EP 2235502 B1. This configuration is described as reducing the risk of air accumulation since the volume within the fibers is much less than the volume within the compartment itself. Water flows from inside to outside. The accumulated filtrate is cleaned by blowing air out of the mouth, which leads to the formation of a reverse flow.

The flow of water from the inside out through a hollow fiber membrane (as described in US 8,852,439 B2) causes large particles to become trapped within the hollow fibers of the membrane. Because of this, there is a need for additional suction pressure or passage pressure, or gravity pressure. Also, when passing through the membrane, large particles lead to the formation of cracks in the fiber wall.

These hollow fiber membrane filters face a common problem. Bacteria enter the filter module and hollow fibers, for example, when air is blown from the mouth to backwash, when backwash occurs due to an external component, due to contamination of the clean side with bacteria, due to insufficient sanitation, or due to environmental pollution. Bacteria remain on the walls of the fibers and begin to form entire colonies. Colonies of bacteria grow on the filtered water side of the membrane when air is blown through the filter mouthpiece, when backwashing occurs with an external component, due to contact of bacteria with the cleaned side, or due to poor disinfection and a contaminated environment. This leads to contamination of the filtered liquid and unsuccessful filtration.

To solve this problem, the method described in US 8,852,439 B2 is used. A bacteriostatic/biocide layer is applied to the outer walls of the filter to prevent bacteria from spreading and contaminating the filtered water. However, the problem is that the biocidal layer is applied only to the filter block (for example, to the outer wall of the filter block), and not to the membrane. This may cause the membrane to become dirty (on the clean side). Also, this biocidal layer is washed away due to erosion and flows out along with the filtered liquid. This reduces the longevity of the antimicrobial function. Biocidal materials (if washed out with filtered water) can be harmful to the human body if consumed.

There is another method to reduce the risk of bacteria growing and spreading inside the filter (for example, due to backwashing or clean side contact with bacteria, contaminated media, or poor disinfection). We are talking about the use of silver nanoparticles. Silver is an antibacterial material that kills 99% of germs. Nano silver particles are washed out of the membrane over time and leave large cavities in its walls, which leads to the penetration of microbes into the membrane. Due to the migration of silver nanoparticles, over time, the antimicrobial properties disappear (see US 7,390,343 and 9,200,086).

In all the filtration devices described above, the porosity of the hollow fibers reaches up to 80%, therefore, in order to carry out the filtration process, additional suction or passage pressure or gravity pressure is required and there is a risk of air accumulation inside the filter.

SUMMARY OF THE INVENTION:

Thus, the purpose of this invention is to improve the quality of filtration by introducing new built-in antimicrobial functions into the membrane. If desired, additional improvements can also be achieved using the present invention, such as improving water flow by eliminating the problem of air accumulation and plugging holes with air bubbles; Reducing the required suction pressure, pass pressure, or gravity head for hollow fibers in a water filtration system. This invention is particularly directed to improving the quality of filtered water and water flow, reducing the required suction pressure, passage pressure or gravity head.

Surprisingly, the inventors discovered that it was possible to create a new membrane with built-in antibacterial properties. Such a membrane can be used in multi-functional, portable, multi-port installations where liquid, such as water, flows from outside to inside through the membrane filter. This means that the invented membrane has built-in antibacterial functions and is able to provide a liquid, such as water, that is free of germs and is safe to drink.

Another object of the present invention is to provide a method for producing hollow fiber membranes with great strength and excellent fractionation function and water permeability.

In this regard, the first aspect of the present invention is to provide a hollow fiber membrane having antibacterial properties for filtering liquids, in which liquid flows in from outside and passes through the porous part of the membrane into the lumen between the hollow fibers, leaving the filtrate outside the membrane, and then the filtered liquid flows out from the other end of the membrane, passing through the hollow fibers.

The hollow fiber membrane of the present invention is characterized in that the outer surface or outer wall of the hollow fibers has hydrophobic properties and the inner surface or inner wall of the membrane has hydrophilic properties.

The hollow fiber membrane of this invention may have a pore size from 0.1 nanometer to 25 nanometers.

The hollow fiber membrane can have a fiber diameter from 0.2 mm to 0.6 mm.

The hollow fiber membrane can have a wall thickness of 1 mm to 2 mm.

The hollow fiber membrane presented in this invention can be characterized in that the outer surface or outer wall of the hollow fiber has hydrophobic properties, and the inner surface or inner wall of the membrane has hydrophilic properties, can have a pore size of 0.1 nanometer to 25 nanometers, diameter fibers from 0.2 mm to 0.6 mm and wall thickness from 1 mm to 2 mm.

Hollow fibers can be made from a polymer or a thermoset polymer. For example, the fibers can be made from polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polythemacrylic acid, polyamide, polyimide, polyether imide and cellulose acetate, as well as mixtures of these materials. The inventors have discovered that the choice of polymers or mixture of polymers influences pore formation and Pure Water Permeability (PWP) and Critical Water Flow (CWF). The production of fibers from polymers allows for the formation of a large number of pores in a given area of the fiber wall, as well as a larger percentage of spaces on the fiber wall. For example, membrane fibers consist of 16-20% polyethersulfone by weight, or 5-20% polyvinylpyrrolidone by weight, or 70-90% n-methyl-2-pyrrolidone by weight, or 10-45% polyoxyethylene glycol by weight. Alternatively, the fibers may also consist of polycarbonates, polyamides, hydrous isopropyl, or any combination of these substances. For example, membrane fibers consist of 10-25% polysulfone by weight, 5-15% polyvinyl pyrrolidone by weight. For example, the fibers consist of 3-25% polyethersulfone by weight and 5-15% polyvinylpyrrolidone by weight.

The fibers can consist of polyethersulfone, as well as ultrason polyethersulfone with a gradation of 6020r. For example, the fibers consist of 12-25% polyethersulfone, 40-90% n-methyl pyrrolidone and 10-45% polyether glycol. Such a composition may also contain lithium chloride (eg, 0.5 to 1.5%).

Fibers can be presented in various compositions. For example, the fibers can form a single-layer membrane, a membrane consisting of several layers, or form a double layer (eg, two arc-shaped sets of fibers opposite each other in a closed system).

Multiple layers may have different properties represented in each individual layer.

A single-layer membrane can be either hydrophobic or hydrophilic. The outer wall of the membrane layer (eg, the side that contacts the water being filtered) may be hydrophobic, and the outer side of the layer or wall (eg, the side that is in contact with the fibers and the filtered liquid) can be hydrophilic. The hydrophobic layer reduces air accumulation and suction pressure. The hydrophobic layer increases fluid flow.

The hydrophilic layer allows the capillary action of fluid to flow through the pores on the fiber walls toward the fiber cavity and reduces the amount of suction pressure, pass pressure, or gravity thrust required.

The fluid may flow from outside to inside (eg, filtration fluid is provided outside the lumen of the fiber duct and flows within the lumen during filtration). Alternatively, the fluid may flow from the inside to the outside.

If the liquid flows from the inside to the outside, the filtrate remains outside the membrane. The membrane is washable for easy cleaning.

The fibers that define the membrane have pores in the walls through which water passes. Numerous pores can cause the fiber to have a cavity with gaps ranging from 70-90% or 80-90%) of the total volume of the fiber wall. The pore size can vary from 0.1 nm to 25 nm in diameter. For use under suction pressure, the pore size can range from 50 nm to 150 nm in diameter.

The membrane fibers in this invention may have a Pure Water Permeability (PWF) of more than 1800 l/m2/hour at a pressure of less than 1 bar and a Critical Water Flow (CWF) of more than 900 l/m2/hour.

The hollow fibers can form arcuate membrane modules with open ends, where liquid flows into the membrane for filtration and filtered liquid flows out through the open ends of the fibers. For example, as described in US Patent No. 5,160,673.

In a preferred embodiment, the fibers should be antibacterial in nature. This means that they are not just coated with an antibacterial substance. In this case, the antibacterial nature of the membrane cannot be easily changed, and there is no risk that it could harm the filter user if it enters the body. This result can be achieved by introducing an antibacterial substance inside a polymer system that forms fibers. The antibacterial substance can be physically enclosed at the site of cross-linking between polymer chains. The antibacterial substance can be chemically introduced at the site of cross-linking between polymer chains. The introduction of an antibacterial substance within the polymer will result in the formation of a polymer with embedded antibacterial properties.

The antibacterial agent may be a metal, a metal salt, or a metal oxide with antibacterial properties. For example, it may be zinc oxide, zinc or zinc salt. Thus, for example, the fibers of the present invention can be considered irreducibly antibacterial when at least one zinc salt is added to a solution or suspension of monomers that are used to synthesize the polymer from which the fibers are formed into an aqueous or organic solvent. Alternatively, at least one antibacterial agent (eg, a zinc salt) can be added during the polymerization reaction of the initial monomers.

When a zinc salt is used to modify a polymer to impart antibacterial properties, the salt can be or is composed of any combination of zinc pyrrolidone carboxylic acid, zinc oxide, zinc hydroxide, zinc pyrrolidone and zinc pyrithione.

The polymer or mixture of polymers into which the antibacterial agent is incorporated may be a combination of the substances listed above to create the fiber. For example, the polymer may be a Polyethersulfone, or a polymer mixture that contains a Polyethersulfone.

The antibacterial polymer in this invention can be characterized by the fact that it releases zinc ions below the permissible limits of 21 ppm.

The antibacterial polymer of the present invention is effective for controlling or eliminating the rapid spread of gram-positive and gram-negative bacteria, for example, Escherichia coli (Gram-negative) and/or Staphylococcus aureus (Gram-positive). Other examples: E. coli or Escherichia coli, golden staphylococcus or Staphylococcus aureus, Pseudomonas or Pseudomonas aeruginosa, Akinetobacteria Baumann or Acinetobacter Baum, Enterobacter Cloka or Enterobacter CL OACAE, candidate white or Candida albicans and types of clostridia or Clostridium species, as well as their combinations.

In order to limit the amount of expensive antibacterial agent and the residual loss of antibacterial agent when released into the filtered water, the entire fiber should not be made of an antibacterial polymer. Substantially the entire outer side of each fiber may contain an antibacterial substance within the substance of the polymer itself or the mixture of polymers that form the fiber. The modified polymer is mixed so that 99% of the total surface area of the membrane is antibacterial in nature. The mixture is made using a process that ensures that 99% of the total surface area of the newly created membrane remains antibacterial even though a small amount of 2.5 to 3% of the modified polymer is mixed with the rest of the polymer or mixture of polymers to create it. Thus, the fibers have antibacterial properties outside and inside.

The antibacterial agent may be a metal oxide or a metal. These may be particles of metal or metal oxide. The antibacterial substance incorporated into the polymer or mixture of polymers may constitute 2-5% by weight of the fiber. The polymer or mixture of polymers without the antibacterial agent may constitute 95-98% of the fiber weight. The polymer or mixture of polymers without the antibacterial agent may be the same polymer or mixture of polymers.

The method of forming such a membrane can result in the formation of a fiber incorporating the characteristics described above.

For example, the inventors have discovered that it is possible to achieve a high percentage of fiber porosity by selecting a suitable pore forming device to participate in the fiber creation process.

Therefore, another aspect of the present invention is a process for creating a hollow fiber membrane with an embedded antibacterial function by taking the following steps:-

a) creating a mixture of polymers or adding a polymer to the mixture using a pore-forming device made of polyethylene glycol (molecular weight 300);

b) flow of the mixture created in point a) through the die together with the precipitant for polymers.

The polymers or mixture of polymers for creating the fibers can be selected from those suggested above in the first aspect of the present invention. As an example, the fibers may consist of 12-25%) polyethersulfone, or 40-90%) n-methyl pyrrolidone, or 10-45% polyethylene glycol. Such a composition may also contain lithium chloride (eg, 0.5 to 1.5%).

Polyethylene glycol may be present in solution; for example, an aqueous solution (for example, 9:1 polyethylene glycol: Aqueous solution, or +/-10%).

The precipitant used in b) may be water.

In addition to optimizing pore formation, the inventors also discovered that it was possible to create fibers with antibacterial properties near the outer wall also embedded in the fiber; In this way, the substance used to introduce antibacterial functions is preserved. This method consists of the following steps:

a) a mixture of an antibacterial substance embedded in a polymer or a mixture of polymers, a polymer or a mixture of polymers without antibacterial properties, a solution for both polymers or mixtures of polymers and a device for forming pores from polyethylene glycol (molecular weight 300);

b) flow of the mixture created in the previous step through the die together with a precipitant for polymers.

In a further aspect of the present invention, a process is presented for creating a hollow fiber membrane having an embedded antibacterial function by taking the following steps:-

a) a mixture of an antibacterial substance embedded in a polymer or a mixture of polymers with a polymer or a mixture of polymers without antibacterial properties using a solvent for both polymers;

b) flow of the mixture created in the previous step through the die together with a precipitant for polymers.

Step b) for all processes of this invention can be carried out at a temperature of from 25 to 80 degrees Celsius, or from 40 to 60 degrees Celsius (atmospheric pressure). The die is necessary for working at high speeds. For example, it can run at 350 to 600 rpm, or 450 to 550 rpm, or 500 rpm.

Polymers have a higher ability to form a solution with a solvent than with a precipitant. Therefore, the solvent and precipitant come into contact with each other in step b), the polymers are released from the solvent and solidified. The rapid solidification of the polymer at speed during ejection from the spinneret forms pores in the created fibers. At the same time, the centrifugal force created by the spinning die and influencing the formation of fibers pulls the polymer with an embedded antibacterial substance onto the outer surface of the forming fiber; this polymer has a higher density than a polymer without an antibacterial substance. Thus, the fiber is formed with pores, and the outer part of the fiber contains a predominant portion of the polymer with embedded antibacterial polymer, and the rest is formed from the polymer without the antibacterial substance.

This process for both aspects of this invention can be used to form the membrane of the first aspect of this invention. Therefore, all of the characteristics of the first aspect of the present invention can also be applied to the following aspects of the present invention. For example, the antibacterial substance may be a metal oxide or a metal. The polymer or mixture of polymers with an embedded antibacterial substance can constitute from 2-5% of the total weight of the polymers in the mixture created in point a).

The polymer or mixture of polymers without the antibacterial agent may constitute 95 to 98% of the total weight of the fiber.

The polymer may also contain or consist of polyethersulfone. N-methyl-2-pyrrolidone can be used as a solvent.

The antibacterial substance embedded in the polymer can be polyethersulfone (for example, ultrason® polyethersulfone with a gradation of 6020r), and the polymer or a mixture of polymers without an antibacterial substance can consist of polyethersulfone (for example, ultrason® polyethersulfone with a gradation of 6020r), polymers can be presented in weight ratio of 3% to 97%.

The polymer or mixture of polymers without the antibacterial agent may be the same polymer or mixture of polymers. The antibacterial polymer may contain metal oxide particles introduced by crosslinking polymer chains.

The membrane may be incorporated into standard liquid filtration devices, such as those described in the illustrative review provided above.

Accordingly, another aspect of the present invention includes a liquid filtration device consisting of a hollow fiber membrane as described in the first aspect of the present invention, where the membrane is placed in a device with at least one supply channel and at least one drain channel. The membrane can be placed in a device with multiple openings for inlet, outlet and backwash. The hydrophilic layer of the membrane supports the capillary action of the liquid through the holes in the fiber walls and directs it to the gaps in the fibers and reduces the required suction pressure, passage pressure or gravity pressure.

BRIEF DESCRIPTION OF DRAWINGS

The present invention is described here by way of example and with reference to the following drawings.

Figure 1 shows hollow fibers (2), capped and sealed fiber ends (3), and a sealed module section (4).

Figure 2 shows nanopores on the fiber wall through which liquid enters the internal channel of the hollow fiber (1) and hollow fibers (2).

Figure 3 shows nanopores on the fiber wall through which liquid enters the internal channel of the hollow fiber; (1), filtered liquid (5), cavities in the walls of the fiber (6), hydrophilic layer (7), point of contact of both layers (8), space between the liquid and fiber formed by the hydrophobic layer (9), large particles, impurities , mechanical impurities (U), hydrophobic layer facing the unfiltered liquid (11), and unfiltered liquid (12)

Figure 4 shows nanopores on the fiber walls through which liquid enters (1), hollow fibers (2), plugged and sealed fiber ends (3), sealed modular section (4), filtered liquid (5), cavities in the fiber walls (6), hydrophilic layer (7), point of contact of both layers (8), space between the liquid and fiber formed by the hydrophobic layer (9), large particles, impurities, mechanical impurities (10), hydrophobic layer facing the unfiltered liquid (11), and unfiltered liquid (12).

Figure 5 shows the ends of the hollow fibers from which the filtered liquid comes out (13), the wall of the sealed modular section (14), and the sealant between the ends of the fibers (15).

Figure 6 shows an enlarged image of the fiber wall taken using scanning electron microscopy (SEM).

Figure 7 shows a cross-section of the fiber wall taken using SEM.

Figure 8 shows a graph of water flow over time obtained from a study of 10 membranes manufactured in accordance with the present invention.

Figure 9 shows the results of an antibacterial study of the fibrous material of the present invention.

DETAILED DESCRIPTION OF THE DEMONSTRATED OPTIONS FOR APPLICATION OF THE INVENTION

Below, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The prospects and possibilities of the present invention and methods for achieving these prospects and possibilities will become apparent with reference to exemplary embodiments, which will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments shown and disclosed below, but may be embodied in various forms. Matters defined in the specification, such as detailed construction and elements, are nothing other than specific details presented to assist those skilled in the art in fully understanding the invention, and exemplary embodiments are defined only within the scope of the appended claims. In the drawings, the dimensions and relative sizes of layers and sections may be enlarged for clarity of explanation.

The term "on", which is used to indicate that an element is on another element located on another layer, includes both the case where the element is located directly on another element or layer and the case where the element is located on another element through another layer or another element. In contrast, the term "directly on" means that the element is directly on another element or layer without interference from any other element or layer. Throughout the description of the present invention, the same reference designations are used for the same elements throughout the various drawings. In addition, the term “and/or” includes the corresponding described elements and combinations thereof.

Spatial-orientational language "below", "above", "top", etc., as depicted in the figures, can be used to facilitate the description of the relationship between an element or constituent elements, and another element, or another constituent element. Spatial statements are to be understood as statements that include various directions of use or operation of an element in addition to the guidance illustrated in the drawings.

In the following description of the present invention, an exemplary embodiment of the present invention will be described with reference to a horizontal view and a side view (sectional view), which are ideal schematic representations. This example form may be subject to change due to production techniques and/or error tolerances. Accordingly, exemplary embodiments of the present invention are not limited to their specific exemplified form, but are subject to variations in form according to manufacturing processes.

Therefore, the places shown in the figures are approximate sizes, and the shapes of the various sectors in the figures are indicated approximately for each element, shape and sector, and do not in any way limit the scope and subject of this invention.

Below, a typical example of the structure of the hollow fiber filter membrane (hereinafter sometimes referred to simply as "membrane") of the present invention will be explained with reference to the accompanying drawings. RICE. 1 is an enlarged photograph of a cross section perpendicular to the longitudinal direction of the membrane, and FIG. 2 - enlarged photograph of the inner surface of the membrane.

The membrane according to the present invention consists of a number of hollow fibers, each of which has an inner and outer surface, and includes a network structure that integrally extends from one surface (for example, the inner surface) to another surface (for example, the outer surface), as shown in fig. 3. The network structure in the membrane does not have empty polymer sections, such as a finger-shaped structure layer having cavities and a void layer.

The membrane of the present invention contains a network structure having an anisotropy in pore diameter such that the membrane on or near its outer surface has a layer with a smaller average pore diameter (hereinafter referred to as "average pore diameter of the outer surface"), compared to the average diameter pores located on the inner surface of the membrane (hereinafter referred to as the “average pore diameter of the inner surface”). The pore diameter, as a rule, gradually increases towards the inner surface of the membrane. In accordance with one embodiment of the invention, it is ensured that more than 99% of the pores have a specified diameter on the outer surface (hereinafter referred to as "average pore diameter of the outer surface").

The membrane of the present invention has a porosity (void content) of 70-90% when the membrane material is polyethersulfone, and depending on the void content, the breaking stress IS is in the range of 2 to 3.5 bar, and the elongation at the gap is up to 70%.

As materials for the hollow fiber membrane of the present invention, polymers of polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polymethacrylic acid, polyimide, polyetheramide, and cellulose acetate can be mentioned, for example. Particularly preferred are aromatic polysulfones, polyacrylonitrile copolymers, polyvinylidene fluoride and aromatic polyetherimides. The polyethersulfone series is particularly preferred.

Another aspect of the present invention also describes a filter device for filtering liquid containing a hollow fiber membrane according to the invention, where the membrane is housed in a shell with at least one supply channel and at least one drain channel. In accordance with the concept of the invention, the hydrophilic layer of the membrane supports the capillary action of liquid through the holes on the walls of the fibers in the direction of the cavity of the fibers and reduces the rate of suction pressure, flow pressure and gravitational pressure.

Essentially, an antimicrobial hollow fiber membrane is made by spinning a polymer mixture at high speed, placing said polymer mixture around the circumference of the base polymers, where the polymer mixture contains 3% antimicrobial embedded polyethersulfone 6020r in the base polyethersulfone containing no antimicrobial agent, making the antimicrobial about 99. 9% surface area of the final product. Because the antimicrobial embedded polymer has a higher density, centrifugal force forces it out and onto the circumference of the base polymer, reducing the cost of manufacturing the product. Antimicrobial polymer is developed by chemically incorporating metal oxide particles into polymers through cross-linking between polymer chains. This creates a polymer that is antimicrobial in nature, the inherent antimicrobial properties of which never leach out or migrate from the polymer to any other contacting substance.

Examples of the present invention will be shown below, but the present invention is not limited to these examples. The methods for studying properties are as follows:

Hollow fiber membranes used as samples for properties studies are in a state of sufficient water impregnation. As for the membrane obtained using polyvinylpyrrolidone as an additive, the membrane was immersed in an aqueous solution of sodium hypochlorite and then washed with hot water, obtaining a membrane that was substantially free of polyvinylpyrrolidone.

Water permeability through a hollow fiber membrane is expressed by the amount of 25 degrees Celsius filtered water that passed through the hollow fiber sample.

EXAMPLE 1

Although preferred embodiments of the present invention have been described for purposes of illustration, those skilled in the art will appreciate that changes, additions, and substitutions may be made to the present invention without departing from the spirit or scope of the invention. Thus, the present invention is intended to cover modifications and variations of the present invention provided they come within the scope of the appended claims and their equivalents.

The device of the present invention is a hollow fiber membrane with a built-in antibacterial function. The membrane received a significant change on a micrometric scale, which led to antiseptic and antibacterial properties. The adhesion and proliferation of bacteria on the surface of the object is slowed down, and the number of microorganisms and bacteria is greatly reduced. This antiseptic/antimicrobial nature of the material is a property of the polymer membrane that never migrates/leaches into the filtered liquid and never decreases over time.

Hollow fiber consists of two layers. The outer layer is hydrophobic and the inner layer is hydrophilic in nature. The hydrophobic layer never allows water to come into physical contact with the membrane, therefore stopping any kind of adhesion to it. The hydrophobic layer makes air intake minimal as external air passage is facilitated by the absence of a layer of water on the outside, hence reducing the required suction pressure and increasing fluid flow. In this case, the inner hydrophilic layer maintains the capillary action of liquid through the holes on the fiber walls towards the cavity of the fibers, thereby reducing the required suction pressure, flow pressure or gravity pressure. The fluid flows in an outer orientation, i.e. filtration occurs when liquid from the outside of the fiber wall passes through its opening and the filtered liquid exits the hollow end of the fiber. Therefore, retaining the unfiltered liquid outside the fiber walls and retaining the filtered liquid inside the hollow fiber makes the membrane of the present invention the only membrane used with an external flow direction and having a hydrophobic layer on the outside and a hydrophilic layer on the inside.

Pores on the fiber walls can have sizes ranging from 0.1 nm to 25 nm. Liquid, especially water, is filtered as it passes into the fiber cavity from openings in the fiber walls on the outside. The fibers form arcuate open-ended membrane modules, sealed and supported such that the arcuate side always faces the liquid entering for filtration and the filtered liquid always exits through the open ends of the fibers. The porosity of the fibers ranges from 70% to 90%.

The antimicrobial embedded polymer is developed by chemically bonding metal oxide particles in a BASF brand of ultrafine polyethersulfone polymer, producing a truly antimicrobial polymer whose antimicrobial properties never wash out and never migrate from the polymer to any other substance in contact with the surface of the polymer, unlike existing antimicrobial membranes , on the surface of which antimicrobial properties have been created by coating it with an antimicrobial substance that can wash out and contaminate substances that come into contact with it. Polyethersulfone is a polymer from which hollow fiber membranes are made.

Porosity is achieved during the manufacturing process of the hollow fiber membrane. The method involves the use of 2 reservoirs connected to the die through flow tubes with a gear pump. Reservoir for sealing solution and reservoir for settling solution. The polymers are mixed with a solvent and are completely dissolved in the sealant reservoir. As soon as the sealing and precipitating solution (also called precipitant) begins to flow through the die, the process of phase inversion begins (the polymer that was dissolved in the solvent will now begin to solidify). This phenomenon can be explained by a simple mass transfer process, once the precipitant and solvent come into contact, the interaction between them acts as a driving force to push the dissolved base polymer out of the solvent, resulting in its resolidification. During this process, pores are created due to the instantaneous (very short, less than a second) demixing, which is too short for the polymer to fully cure. Consequently, as the polymer begins to leave the solvent and solidify, the instantaneous demixing results in some discontinuities in the solidifying polymer structure and these discontinuities (gaps) are ultimately pores, and it is this entire collection of pores that gives the fiber its porosity. The fiber formation process is carried out at 50 degrees Celsius, at atmospheric pressure, and with the spinneret operating at 500 rpm. 3% of the total polymer mass is derived from a polymer with embedded antibacterial properties, while 97% is a polymer without embedded antibacterial properties.

Example 2: Pore Formation

The sealing solution/polymer solution is created by mixing the components listed in the table below. The following precipitating solution/inner solution was added to the mixture and mixed well. The mixture was then passed through a spinneret along with water to form hollow fibers.

Sealing solution / Polymer solution

Polyethersulfone 15%

Polyethersulfone Ultrason® E6020Р

Polyethylene glycol 38%

Lithium Chloride 1.5%

H2O 2%

N-methyl-2-pyrrolidone 43.5%

Precipitating solution / Internal solution

Polyethylene glycol (9:1)

Coagulant

100% water

Through testing and benchmarking the performance of these fibers, it has been found that fibers created using the process described above are far superior to the fibers currently in use and described in the illustrative materials above.

When polyethylene glycol is used as a precipitating solution and to form pores in the sealant, due to its high viscosity and fluidity, it imparts certain structural properties to the resulting fibers. In particular, the fibers usually have a well-defined finger-like porous structure, and therefore have straight and well-defined channels throughout the thickness of the fiber, as shown in Fig. 6 and Fig. 7, figure, which shows the wall thickness using SEM (Raster Scanning Electron Microscopy) technology, where the fibers are studied at cross-sectional locations.

Pure Water Permeability (PWP): Pure water permeability, also known as pure water flux, is determined by the volume of water that passes through a membrane per unit time, per unit area, and per unit intermembrane pressure. This property indicates the effort required to create permeability in the membrane and can be used to compare the initial performance of the membrane. This analysis, however, does not provide any data on the performance of the material over long periods of time, so it is useful to also look at the Critical Water Flow (see Persson, Kenneth M., Vassilis Gekas and Gun Tragard. "Studying membrane compaction and its effect on permeability water during ultrafiltration." Journal of Membranes and Membrane Technologies 100, Issue 2 (1995): 155-162).

Critical Water Flow (CWF): Either the flow of water at which the intermembrane pressure begins to deviate from the pure water line (a strong form of critical flow) or when the first flow of water forms irreversible fouling on the membrane surface. The critical flow may have the following general definition: the “first” flow of water at which contamination becomes predominant; it is different from the Limiting Flow (the "last" available water flow), (see Bacchin, Patrice, Pierre Aymard, and Robert W. Field, "Critical and Steady Flow: Theory, Experiments, and Applications." Journal of Membranes and Membrane Technologies 281, no. 1 -2 (2006): 32-69).

10 separate fiber samples made according to the method described above were created and used for 10 different membranes. The membranes were then tested to establish Clean Water Permeability (PWP) and Critical Water Flow (CWF). The membranes were tested as follows:

Pure water permeability experiments were conducted using deionized water. Each module was immersed in deionized water for 24 hours, followed by a 1.5 hour experiment to eliminate the effect of residual glycerol on the hollow fiber membrane before sample collection. The UV filtration device is designed to evaluate the permeability of pure water and the protein retention rate, which is shown in detail (see K. S. Feng, B. Shi, G. Li, Y. Wu, Preparation and properties of microporous polyvinylidene fluoride carbon monoxide-tetrafluoroethylene membrane ) (F2.4) for membrane distillation, Journal of Membranes and Membrane Technologies 237 (2004) 15-24). With an intermembrane pressure of 1 bar and a feed solution at 20 degrees Celsius, all experiments were carried out in hollow fiber modules with a cross-flow system. Two modules were prepared for each hollow fiber sample.

The permeability of clean water was obtained as follows:

When pure water passes through the membrane and the parameters are calculated using the equation above, each parameter is tabulated and a time-parameter diagram is created. For a long period of time (in our case it is more than 5 hours), the permeability of pure water begins to stabilize and express the value of the critical water flow for the membrane. The apparatus used to test the permeability of pure water on fibers can be represented by the following diagram:

The results and important test conditions are provided in Table 1 below. The test was carried out at normal temperature and pressure.

Table 2 provides an overview of the Clean Water Flow at 5 minute intervals over a 120 minute period for each membrane. The results are described in Figure 8.

From these results it is clear that there is a certain consistency for all samples. It can also be concluded that the initial permeability of pure water is higher compared to standard fibers. However, after prolonged testing, the parameters begin to deteriorate and stabilize at one point (where the graph becomes straight and follows a constant slope curve), which determines the critical water flux for each membrane, and the value of the critical water flux is used as a design factor when such membranes are put into practical use . However, it can be noted that in all samples the critical water flow fluctuates between 800 and 900 l/m2/h, which is an advantage of the fibers described in this invention, since in this case less pressure is required to flow the same amount of water through the fibers. compared to standard options, which helps reduce costs.

Example 3: Testing the Antibacterial Properties of the Surface of Membrane Fibers

A hollow fiber membrane was created in accordance with Example 2, but a zinc salt was added inside the polymer.

The membrane was then tested to block two types of bacteria (Escherichia Coli ATCC 8739 (Gram-negative) and Staphylococcus Aureus 6538 (Gram-positive)) using standard international methods for assessing the antibacterial properties of polymer surfaces. The results can be found in the drawings of bacterial cultures grown on Petri dishes and shown in Fig. 9. The results are shown below.

Table 3

From the table you can see that the bacteria blocking zone in tests that were carried out on polymer fiber (for example, polymer with zinc salt) coincides with the geometry of the fiber sample placed in a Petri dish; This shows almost complete elimination of bacteria on portions of the disc where fiber was applied. This is confirmed by the decrease in CFU/ml, which is presented in Table 3 for the original inoculum compared to the value for the twisted polymer fiber.

Analytical method:

Hollow fiber spun antibacterial polymer Polyethersulfone, prepared as described above, was analyzed to determine the effectiveness of the polymer against the major strains of microorganisms defined by legislation defining standards for plastics that come into contact with the skin.

The product was analyzed using 2 strains of microorganisms (E. coli or Escherichia Coli ATCC 8739 (Gram-negative) and Staphylococcus aureus or Staphylococcus Aureus 6538 (Gram-positive)) using standard international methods for assessing the antibacterial properties of non-porous plastic surfaces.

An initial incubation control polymer was created MICROBIAL inoculum at a temperature of 37° Celsius, Reduction of bacterial strains (CFU/ml) in 24 hours (CFU/ml) (CFU/ml) reduction of the number of microorganisms Vo Escherichia (Escherichia coli) 2.5 × 106 6.2 × 107 1.0×107 0.79 83.87% coli Staphylococcus (Staphylococcus aureus) 1.7×106 2.3×107 1.4×106 1.2 93.91% Aureus

The initial bacterial solution was diluted to achieve a known bacterial concentration, expressed as colony nascent groups of CFU/ml. The analyzed fibers were divided into parts to ensure optimal sizes for analysis. These parts were treated against microbial strains, covered with sterile polyethylene film and placed in an incubator at 37±1°C for 24 hours. At the end of the incubation period, the samples were washed with a neutralizing solution, on which the number of microbes was detected.

The results showed that after 24 hours of incubation at 37 degrees Celsius, the zinc-treated polymers reduced the number of bacteria by 83.870 (in the case of Escherichia coli) and by 93.91%) (in the case of Staphylococcus aureus).

Figure 9. Explanation:

As shown in the figure, a total of 6 Petri dishes were taken - 2 sets of 3 pieces.

The three bowls on top were impregnated with nano silver particles for an antibacterial effect, and the three bowls on the bottom were equipped with a sample of fibers from this invention (spun hollow fiber membranes). As can be seen in the figure, silver nanoparticles washed out in three Petri dishes and migrated outside the substance to eliminate bacteria around the sample. However, the growth of bacteria on the three lower Petri dishes was blocked on the surface of the sample, which provides evidence to support the claim that the substance with antibacterial properties is not leached from the material used in this invention.

Claims (36)

1. A hollow fiber membrane having inherent antimicrobial properties for filtering liquids, comprising a plurality of porous hollow membrane fibers, wherein the hollow membrane fibers include a polymer or mixture of polymers including an antimicrobial substance physically enclosed and chemically bonded at the site of cross-linking between the polymer chains, giving the fibers antimicrobial nature, and at the same time the hollow fiber membrane is designed so that the liquid flows from the outside of the fibers of the membrane and passes through the porous membrane into and along the cavity of the fibers, so that the retentate remains outside the membrane and so that the filtered liquid (filtrate) flows out from the hollow end of the fibers. 2. The hollow fiber membrane having inherent antimicrobial properties according to claim 1, wherein the hollow fibers are formed from a polymer or a thermoset polymer. 3. A hollow fiber membrane having inherent antimicrobial properties according to claim 1 or 2, wherein the polymer or mixture of polymers from which the hollow membrane fibers are formed consists of or contains from 12 to 25% polyethersulfone, or 5-20% polyvinylpyrrolidone, or 70 -90% N-methylpyrrolidone solution, or 10-45% polyethylene glycol, or fibers containing polycarbonates, polyamides and aqueous isopropyl or any combination of the above substances. 4. The hollow fiber membrane having inherent antimicrobial properties according to claim 1 or 2, wherein the fibers consist of or contain 10-25% polysulfone or 5-15% polyvinylpyrrolidone. 5. The hollow fiber membrane having inherent antimicrobial properties according to claim 1 or 2, wherein the fibers consist of or contain 3-25% polyethersulfone or 5-15% polyvinylpyrrolidone. 6. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-5, where the fibers form a single-layer membrane. 7. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-5, where the fibers form a membrane of more than one layer. 8. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-5, where the fibers form a two-layer membrane. 9. The hollow fiber membrane having inherent antimicrobial properties according to claim 6, wherein the single layer membrane is either hydrophilic or hydrophobic. 10. The hollow fiber membrane having inherent antimicrobial properties according to claim 8, wherein the two-layer membrane is either hydrophilic or hydrophobic. 11. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 6-8, where the outer side or wall of the membrane layer is hydrophobic and the inner side or wall of the membrane layer is hydrophilic. 12. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 9-11, where the hydrophobic layer reduces the need for air accumulation and suction pressure. 13. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 9-12, where the hydrophobic layer increases water flow. 14. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 9-13, where the hydrophilic layer maintains the capillary action of the liquid through the pores on the fiber walls towards the cavity of the fibers and reduces the required suction pressure, passage pressure or gravity pressure. 15. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-14, where the membrane is washable. 16. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-15, where the hollow fiber membrane contains fibers having a porosity range from 80 to 90% of the fiber wall volume. 17. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-16, characterized in that the pores of the hollow fiber membrane are in the range from 0.1 to 25 nm in diameter. 18. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-16, characterized in that the pores of the hollow fiber membrane are in the range of 50 to 150 nm in diameter for use under suction pressure. 19. A hollow fiber membrane having inherent antimicrobial properties according to any one of claims. 1-18, in which the hollow fibers form an arcuate membrane module with open ends, where the liquid entering the membrane for filtration and the filtered liquid exit through the open ends of the fibers. 20. The hollow fiber membrane having antimicrobial properties according to claim 1, characterized in that the antimicrobial substance is a metal oxide, a metal salt or a metal, for example a zinc salt. 21. Hollow fiber membrane with antimicrobial properties according to claim 20, characterized in that the antimicrobial substance is built into a polymer or a mixture of polymers. 22. Hollow fiber membrane having antimicrobial properties, according to any one of paragraphs. 20 or 21, in which the polymer or mixture of polymers with an antimicrobial substance constitutes from 2 to 5% by weight of the fiber. 23. Hollow fiber membrane having antimicrobial properties, according to any one of paragraphs. 20-22, further comprising a polymer or mixture of polymers, in which or in which there is no antimicrobial substance, in an amount of from 95 to 98% by weight of the fiber. 24. The hollow fiber membrane having antimicrobial properties according to claim 23, wherein the polymer or mixture of polymers with and without the antimicrobial agent is the same polymer or mixture of polymers. 25. A method for producing a hollow fiber membrane having inherent antimicrobial properties, according to any one of claims. 1-24, including the following steps: a) mixing a polymer with an embedded antimicrobial substance or a mixture of polymers with an embedded antimicrobial substance with a polymer or a mixture of polymers without an antimicrobial substance, with a blowing agent containing polyethylene glycol and other additives, with a solvent for all components; b) passing the mixture obtained in step a) through a die together with a polymer precipitant. 26. The method according to claim 25, in which step b) is carried out at a temperature from 25 to 80 degrees Celsius. 27. Method according to any one of paragraphs. 25 or 26, wherein the antimicrobial agent is a metal oxide, a metal salt or a metal. 28. Method according to any one of paragraphs. 25-27, in which the polymer or mixture of polymers, which includes an antimicrobial substance, constitutes from 2 to 5% of the total weight of polymers in the mixture formed in step a). 29. Method according to any one of paragraphs. 25-28, in which the polymer or mixture of polymers, in which there is no antimicrobial substance, constitutes from 95 to 98% by weight of the fiber. 30. Method according to any one of paragraphs. 25-29, in which the polymer into which the antimicrobial agent is incorporated is a polyethersulfone and the polymer or mixture of polymers in which the antimicrobial agent is absent is a polyethersulfone, the polymers being present in a weight ratio of from 3 to 97%. 31. Method according to any one of paragraphs. 25-30, in which the polymer or mixture of polymers with and without an antimicrobial agent is the same polymer or mixture of polymers. 32. Method according to any one of paragraphs. 25-31, wherein the antimicrobial agent contains metal oxide particles incorporated therein by cross-linking between polymer chains. 33. A device for filtering liquids containing a hollow fiber membrane according to claims. 1-24, the device including a housing for the membrane, where the housing contains at least one supply channel and at least one drain channel. 34. The device according to claim 33, in which the housing contains a plurality of openings for the inlet, outlet and return drain channels.